一种桩承式路堤沉降的简化计算方法
Simplified Method for Analysing Pile-Supported Embankment Settlements over Soft Soil

针对路堤荷载作用下桩土复合地基的沉降计算，传统方法主要是把沉降分为加固区沉降和非加固区沉降两部分来考虑，存在着计算假设与实际不符、部分参数取值依赖于经验和无法较好考虑成层场地非均质性等缺点.基于此，通过引入均匀系数来考虑地基表面荷载分布的不均匀性，改进了正方形和三角形布桩条件下Hewlett&Randolph土拱模型，在此基础上，考虑桩土相互作用提出了一种桩土复合地基沉降的简化分析方法.该方法首先根据土拱模型和Vesic球孔扩张法分别计算桩顶、地基表面荷载和桩端力；然后采用可以考虑多土层的非均质地基土情况修正Mindlin解求得桩端力、地基表面荷载和桩侧摩阻力在地基内任意点引起的附加应力；其次通过分层总和法计算附加应力引起的沉降；最后将各分项沉降进行组合即可得到桩顶和地基表面沉降.将该计算方法结果与现场实测和数值分析结果进行对比，研究结果发现：简化分析方法的计算精度基本保持在5.0%~14.4%，计算精度能够满足工程需求.
：A method for the settlement of pile-supported embankments over soft soil with due consideration of soil arching and pile-soil interactions is proposed. Traditionally, settlements comprising composite foundations and built under embankments are usually divided into two parts-reinforced and un-reinforced. However, when calculating the settlements, some assumptions which are somewhat disaccordance with the truth are made. In addition, some parameters employed in some traditional methods are uncertain and the nonuniformity of layered site is hardly to be considered. Therefore the access to a more accurate analytical results is restricted.Based on the arching model proposed by Hewlett and Randolph, a uniform coefficient has herein been incorporated to allow for evaluation of non-uniform vertical stresses acting on the soft ground. This, in turn, serves to deduce solutions for the arching effect in square and triangular pile configurations. In the method proposed, the load acting on the pile head and the resulting subsoil reaction could be evaluated through analysis of the soil-arching effect. The load at the pile tip can be calculated by employing the spherical cavity expansion theory. Subsequently, additional stresses induced by the load at the pile tip, subsoil reaction, and skin friction acting on the pile could be obtained through use of revised Mindlin's solution by considering the ground to be comprised of multi-layered soil. Settlement results, obtained by accounting for additional stresses, could then be calculated using the layer-wise summation method. Settlements of the pile head and ground surface could, thus, be evaluated by superimposing different partial settlements. The proposed method serves to analyse pile-head as well as ground-surface settlements and offers the advantage that the parameters employed in the analysis could be conveniently adopted and that the deduction procedure is concise. Comparison of results obtained using the proposed method with observed data and numerical results demonstrates that the proposed method is capable of accurately estimating the settlement of piles as well as ground surface of